Determine the role of the intestinal microflora in the metabolism of biologically significant estrogens in women who are at high and low risk to develop breast cancer. We will collect urine, plasma, and feces from five different groups of women and will measure the levels of various biologically significant estrogens. In addition, fecal specimens will be collected in order to extract enzymes from the intestinal microflora to test their ability to modify estrogens by deconjugation, dehydroxylation, hydroxylation, aromatization, and reduction of keto groups.